1. Field of the Invention
The present invention relates to a vehicle body frame structure made of an aluminum alloy material.
2. Description of the Related Art
An aluminum alloy material has recently been used to form a vehicle body frame structure so as to decrease the weight thereof. However, the aluminum alloy material is not easily spot-welded and is expensive when used to form a monocoque-type vehicle body. Thus, a welded space frame type vehicle frame was made of a hollow material by extrusion molding. In this case, ordinarily, a side sill is located at an elongate position in the side of the floor of the passenger compartment. Further, a rear side frame is located at an elongate position inside the rear wheel. Furthermore, a front end of the rear side frame and a back end of the side sill are connected with a side of a rear cross member. However, in the above case, the coupled locations of the rear side frame with respect to the rear cross member and the side sill are offset from each other in the direction of the width of the vehicle. Therefore, it is necessary to enlarge a cross sectional area of the rear cross member or the side sill so that the kick-up portion not to deform into the passenger compartment if the vehicle experiences a rear end collision. However, if the area is enlarged, the dwelling comfort or ingress/egress ease deteriorates.